1. Field of the Invention
This invention relates to a cathode ray tube positioning device employed in a production process for producing a cathode ray tube for e.g. a monochromatic television receiver or a color television receiver.
2. Description of the Prior Art
The cathode ray tube employed in, for example, a color television receiver, is produced through a number of process steps, including the step of coating the inner surface of the panel with carbon or phosphors and producing a phosphor surface by light exposure and development and the step of attaching a shadow mask to the panel provided with the phosphor surface.
For carrying out these process steps, the cathode ray tube needs to be positioned accurately. For example, in the process step of preparing the phosphor surface, the panel needs to be positively secured in position because high precision is required as to the width and the relative position of carbon stripes and phosphor stripes. Above all, in the process step of producing the phosphor surface, a higher accuracy is required as to panel positioning because the operations of light exposure and development need to be performed repeatedly. Even after the phosphor surface is completed, it is necessary to position the panel or the cathode ray tube accurately.
As a conventional cathode ray tube positioning device, there is known a device composed of fastener pins for securing the panel transported by rolls, an abutment roll unit for abutment against an alignment section on the lateral surface of the panel, and a counter roll unit facing the abutment roll unit for positioning and securing the panel in cooperation with the abutment roll unit.
For positioning the cathode ray tube by the above-mentioned positioning device, the panel transported by the rolls or the like is supported by four fastener pins, with a front panel surface as a supporting surface.
In this state, air is ejected against the panel via a center hole of a suction pad intimately contacted with the front panel surface.
The result is that the panel is subjected to a reduced force of friction relative to the fastener pins due to the air directed thereto from the lower side.
The abutment roll unit is abutted against the alignment section on the lateral surface of the panel so that the panel is supported in abutment against the abutment roll unit by the counter roll unit provided facing the abutment roll unit for positioning the panel.
In the above-described device, a small-sized cathode ray tube can be positioned fairly accurately. However, a large-sized cathode ray tube cannot be positioned accurately because of weight. That is, the large-sized cathode ray tube is so heavy that, even when an air blower is used for ejecting air for reducing the force of friction between the stationary pin and the front panel, the counter roll unit needs to be pressed with a larger pressure. The result is that fine positioning of the cathode ray tube is difficult to achieve is that the positioning accuracy of the cathode ray tube is lowered. Although air blowing, for example, may be intensified for combatting this problem, the air blowing noise is increased prohibitively. In the above-described device, the front panel surface tends to be grazed due to contact with the fastener pins to produce flaws. In large-sized cathode ray tube, such flaws tend to be so severe that the production yield may be lowered significantly.